Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Link chain, in particular bush chain
The present invention relates to a link chain, in particular a bush
chain, preferably a conveyor chain, according to the preamble of
claim 1.
A link chain, in particular a bush chain, is constructed essentially from
two elements which are lined up beside one another in an endless
manner. These elements are also referred to as an inner link and
outer link. An outer link usually comprises two outer link plates, which
are fixed to one another by two pins. An inner link is usually made up
of two inner link plates and two bushes, which along with the pins of
the adjacent outer links form a respective chain joint. These joints
allow the link chain for example to wrap around the chain wheels
located in the drive train.
In addition to numerous other applications, link chains lend
themselves to be used as a conveyor chain, wherein rollers are fitted
on the extended pins or the bushes and the link plates, or at least
some link plates, are intended to be connected to add-on parts, for
example platforms. For this purpose, the link plates are designed, for
example, in the form of angled link plates which, alongside the actual
link plate, have an extension arm, to which the add-on parts can be
connected. This results, in cross section, in a for example L-shaped
link plate.
In the case of various articles and raw materials being conveyed, the
link chains are subjected to the action of the article itself and to the
influences of the environment and surroundings. It is possible here for
dirt and other substances and liquids to penetrate into the chain joint
and contribute there to relatively quick and increased wear.
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It is therefore often the case in such cases that chain joints are
sealed. A construction of a corresponding link chain or sealing
arrangement has been disclosed, for example, by DE 2726033 A1 or
DE 3629591 A1.
It can be seen in figure 1 of DE 2726033 A1 that the sealing lip of a
seal outlined there butts, and provides sealing, against the end side
of the bush. A spacer ring is intended to prevent the seal from being
destroyed by mechanical overloading. The spacer ring is located
between the bush and outer link plate.
Such a seal has the advantage that the joint is sealed in an "oil-tight"
manner. This means that the chain joint can be filled with lubricants,
such as oil or grease, and can thus be operated for a large period of
time without any further maintenance. The joints are thus permanently
lubricated. The oil is introduced via conventional lubricating bores in
the pin.
Such link chains, however, are beset by a number of disadvantages.
The distance between the bush and outer link plate can give rise to a
not inconsiderable amount of bending stress in the pin under load.
Furthermore, an amount of pin deflection and therefore relatively
pronounced edge pressure between the bush and the pin are to be
expected. The bending of the pin and edge pressure, in turn, can
result in reduced fatigue strength and a maximum-transfer level of
tensile strength for the chain. Overall, a relatively large amount of
wear and a relatively low breaking strength are to be expected.
Furthermore, the bush or the end side of the bush has to perform its
tasks as sealing surface and bush. This requires a compromise in
terms of the properties which are necessary in each case, in
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particular in respect of material and production, and this sometimes
results in high-outlay production and increased material costs.
This also gives rise to a reduced contact surface area between the pin
and outer link plate, in the case of the outer link plate having a cutout
adjacent to the aforementioned contact surface area. Since the outer
link plate is usually pressed onto the pin, a correspondingly smaller
contact or joining surface area is the result, it therefore being
possible for the press fit to transmit fewer forces and moments.
Moreover, there is an increase in the bearing pressure here in the
link-plate hole.
Accordingly, the object of the present invention is to propose an
improved link chain, in particular to propose a link chain which
overcomes at least one of the disadvantages outlined above, and
preferably all of them, but at least provides improvements. In
particular, the intention is to propose a link chain in which the
bending stress and/or edge pressure to be expected in/on the pin can
be reduced even just by design measures and/or in which, as far as
the selection of material for, or the machining of, the bush is
concerned fewer comprises, if any at all, resulting from the use of the
end side of the bush as sealing surface have to be accepted, and/or
in the case of which preferably the entire link-plate thickness
contributes to the contact surface area.
This object is achieved according to the invention by a link chain
having the characterizing features of claim 1. Since the sealing
arrangement is arranged between the inner link plate and the outer
link plate, the sealing arraignment can be shifted to a certain extent
out of the region of the bush, or end side of the bush, into the region
of the link plates. An oil-tight or lubricant-tight chain joint can be
realized nevertheless. It is no longer the case, however, that the
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sealing arrangement butts against the end surface of the bush. Since
the end side of the bush is then no longer required as sealing surface,
there is no longer any need to accept compromises, for example as
far as surface machining, selection of material, etc., are concerned, in
respect of the bush or the end side thereof. In addition, the distance
between the bush and outer link plate can be shortened, and
therefore the bush can cover over the pin as far as the outer link
plate. This helps to achieve better force transmission between the pin
and bush and, generally speaking, the pin will undergo less
deflection. There is also no need to provide, for example, a cutout,
which reduces the contact surface area between the outer link plate
and the pin. The entire thickness of the link plate can be used as a
contact surface area. Since the sealing arrangement is arranged
between the inner link plate and the outer link plate, and no longer
between the end side of the bush and the outer link plate, the
accommodating space for the seal is at a greater radial distance from
the bush. This gives rise to a larger amount of "free space" between
the seal and bush. This residual space can be filled with oil. Generally
speaking, this gives rise to a relatively large lubricant reservoir, which
extends the service life and maintenance intervals of the link chain.
Further advantageous configurations of the proposed invention can be
gathered, in particular, from the features of the dependent claims.
The subjects or features of the various claims can be combined with
one another, in principle, as desired.
In an advantageous configuration of the invention, provision may be
made for the sealing arrangement to be arranged radially outside the
bush. Accordingly, the sealing arrangement no longer butts against
the end surface of the bush. Since the end side of the bush is then no
longer required as sealing surface, there is no longer any need to
accept compromises, for example as far as surface machining,
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selection of material, etc., are concerned, in respect of the bush or
the end side thereof. In addition, the distance between the bush and
outer link plate can be shortened, and therefore the bush can cover
over the pin as far as the outer link plate. This helps to achieve better
force transmission between the pin and bush and, generally speaking,
the pin will undergo less deflection. There is also no need to provide,
for example, a cutout, which reduces the contact surface area
between the outer link plate and the pin. Since the sealing
arrangement is arranged between the inner link plate and the outer
link plate, and no longer between the end side of the bush and the
outer link plate, the accommodating space for the seal is at a greater
radial distance from the bush. This gives rise to a larger amount of
"free space" between the seal and bush. This residual space can be
filled with oil. Generally speaking, this gives rise to a relatively large
lubricant reservoir, which extends the service life and maintenance
intervals of the link chain.
In a further advantageous configuration of the invention, provision
may be made for the bush to have a projection projecting from the
inner link plate in the direction of the outer link plate. Such a
projection can be used to receive a thrust washer, which in turn may
be part of the sealing arrangement. In addition, the projection can be
used to achieve the situation where the pin is covered over to the
maximum extent by the bush, and therefore, generally speaking,
relatively large loads, in particular bending loads, can be absorbed by
the pin. The projection acts, as it were, as a reinforcement for the pin.
In addition, the projection can be used as a spacer ring for spacing
the outer link plate apart from the inner link plate, in which case there
is no pressing need for a separate spacer ring to be inserted.
In a further advantageous configuration of the invention, provision
may be made for the end side of the bush to be arranged, in
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particular, directly in front of the outer link plate. There is, for
example, no seal provided between the end side of the bush and
outer link plate. Accordingly, the outer link plate can be supported on
the end side of the bush, and this likewise helps to absorb relatively
high bending loads acting on the pin. This also results in less bending
of the pin and/or less edge pressure between the pin and bush.
However, there is preferably a certain amount of play between the
end side of the bush and outer link plate, so that the chain joint can
rotate freely.
In a further advantageous configuration of the invention, provision
may be made for the sealing arrangement to comprise a seal and a
seal-accommodating space. The seal-accommodating space serves
for accommodating the seal. Furthermore, the seal-accommodating
space can be filled with lubricants, for example oil, grease, etc., and,
accordingly, it serves as a reservoir for the lubrication of the chain
joint.
In an advantageous configuration of the invention, provision may be
made for the seal-accommodating space to be formed from a thrust
washer and an accommodating washer. This variant constitutes one
option for configuring the seal-accommodating space between the link
plates. It is advantageously possible, in the case of this variant, for
the sealing surface for the seal to be formed entirely by the thrust
washer. To this extent, no particular attention has to be paid to the
configuration of the link-plate surface as sealing surface, and there is
therefore no need here for the link plate to be machined in any
specific way. Accordingly, the accommodating washer can be
designed for accommodating and/or retaining the seal.
In a further advantageous configuration of the invention, provision
may be made for the seal-accommodating space to be formed from a
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thrust washer and an annular cutout, in particular in the outer link
plate. This variant constitutes a further option for configuring the
seal-accommodating space between the link plates, the separate
accommodating washer being replaced, to a certain extent, by an
annular cutout in one of the link plates. The advantage of this
configuration resides in space being created. The inner and outer link
plates can be located closer together, since part of the
seal-accommodating space is incorporated in the link plate.
In a further advantageous configuration of the invention, provision
may be made for the thrust washer or the accommodating washer to
be fitted onto the projection of the bush. The projection of the bush,
projecting from the inner link plate, can be used as a connection
means for the thrust washer or the accommodating washer. This
provides for straightforward and effective installation of the seal
accommodated in the seal-accommodating space.
In a further advantageous configuration of the invention, provision
may be made for a ring, in particular a metal ring, to be arranged in
the seal-accommodating space. The metal ring can form, together
with the seal, a labyrinth seal. The ring can also increase the size of
the seal-accommodating space.
In a further advantageous configuration of the invention, provision
may be made for the link plates to be formed from semifinished
products, in particular flat material or sheet metal. In the case of link
plates being made from semifinished products, in particular flat
material or sheet metal, even small numbers of items can be produced
cost-effectively. Furthermore, it is possible to realize more or less any
desired contours and sizes. Customer requirements can be met, and
one-off production operations can be realized, easily and
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advantageously. However, it is likewise conceivable for the link plates
to be forged link plates.
In a further advantageous configuration of the invention, provision
may be made for the bush and/or the pin to be provided with a
lubricant-introduction opening. Accordingly, it is possible for the chain
joint can be filled with lubricant via said lubricant-introduction
openings.
In a further advantageous configuration of the invention, provision
may be made for the bush and/or the pin to be provided with
lubricant-accommodating devices, in particular grooves, surfaces or
bores. The lubricant-accommodating devices, which may be arranged,
for example in the form of grooves, surfaces or bores, on the pin or
the inner wall of the bush, serve as a reservoir for the lubricant within
the chain joint. Ultimately, the link chain thus requires less
maintenance or, possibly, even becomes maintenance-free.
In a further advantageous configuration of the invention, provision
may be made for the seal-accommodating space to be filled with a
lubricant, in particular oil or grease. The seal-accommodating space
can serve as a lubricant reservoir for the chain joint and ensure the
long-term lubrication of the latter.
Provision can advantageously be made here for the bush to have
radial grooves on the end side. As a result, lubricant can be
transported from the seal-accommodating space into the
lubricant-accommodating devices, and vice versa.
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Further features and advantages of the present invention will become
clear by way of the following description of preferred exemplary
embodiments, with reference to the accompanying figures, in which:
figure 1 shows a perspective illustration of a link chain according to
the invention;
figure 2 shows a cross-sectional illustration of a link chain
according to the invention with a cutout and a thrust
washer, which form the seal-accommodating space;
figure 3 shows an enlarged illustration of a detail from figure 2;
figure 4 shows a cross-sectional illustration of a further embodiment
of a link chain according to the invention, this time with a
thrust washer and an accommodating washer, which form
the seal-accommodating space;
figure 5 shows a cross-sectional illustration of a further embodiment
of a link chain according to the invention, this time with a
cutout and a thrust washer accommodated in a cutout,
which form the seal-accommodating space;
figure 6 shows a cross-sectional illustration of a link chain
according to the invention with a cutout and a thrust
washer, which form the seal-accommodating space;
figure 7 shows a perspective illustration of a thrust washer,
respectively designed with a channel-like cross section and
with an L-shaped cross section;
figure 8 shows a perspective illustration of an accommodating
washer;
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figure 9 shows a perspective illustration of a link plate with cutouts
and a respective ring inserted therein; and
figure 10 shows a perspective illustration of a link plate with cutouts.
The following reference signs are used in the figures.
1 Inner link plate
to 2 Outer link plate
3 Bush
4 Pin
5 Roller
6 Connection element
7 Thrust washer
8 Cutout/annular groove
9 Seal
10 Ring
11 Seal-accommodating space
12 Accommodating washer
13 Cutout
31 Projection
32 Groove
41 Shoulder
42 Channel
43 Lubricant-introduction opening
44 Lubricant-accommodating device
The construction of a link chain is sufficiently known to a person
skilled in the art. A link chain, in particular a bush chain, is
constructed essentially from two elements which are lined up beside
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one another. These elements are also referred to as an inner link and
an outer link. An outer link usually comprises two outer link plates 2,
which are connected to one another by two pins 4. An inner link is
usually made up of two inner link plates 1, which are connected to
one another by means of two bushes 3. A respective bush 3 and a pin
4 of adjacent chain links, the pin being inserted into the bush, form a
chain joint. These joints allow the link chain for example to wrap
around the chain wheels located in the drive train. The
aforementioned embodiment forms a straightforward link chain. It is,
of course, also conceivable to have more link plates per inner link and
outer link. It is also conceivable to have fewer link plates per chain
link, for example in the case of a bar-link or block-and-bar chain. The
chain according to the invention can be provided with rectilinear or
angled link plates. In particular all configurations of a bush conveyor
chain are possible.
In an application as a conveyor chain, preferably extended pins 4 or
bushes 3 are provided with corresponding rollers 5 and/or the link
plates, in particular the inner link plates 1 and/or the outer link plates
2, are provided with corresponding connection elements 6. It is then
possible for transport devices, for example platforms or the like, to be
connected thereto.
It is possible to use in principle metallic materials for the link plates,
pins and bushes. However, non-metallic materials such as
high-strength plastics, etc., are also conceivable. It is possible for the
link plates to be produced from semifinished products, in particular
flat material or sheet metal, or also in the form of forgings or castings.
It is also possible to use injection molding or 3D printing from plastic
or other suitable materials. Provision is also preferably made for the
end of the pin to be provided with a shoulder 41 for connection to the
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outer link plate 2. The resulting stop provides for very precise
installation of the outer link plates 2.
The region which is essential to the present invention is the region
between an inner link plate 1 and an outer link plate 2. To this extent,
the link chain according to the invention comprises at least one inner
link plate 1 with a bush 3 and also one outer link plate 2 with a pin 4.
The pin 4 is inserted into the bush 3 and forms a chain joint. The link
chain according to the invention also has a sealing arrangement,
which is provided for sealing the chain joint formed from the bush 3
and pin 4.
The invention provides for the sealing arrangement to be arranged
between the inner link plate 1 and the outer link plate 2, in particular
radially outside the bush 3.
A sealing arrangement of a link chain according to the invention
essentially comprises a seal-accommodating space 11 and a seal 9,
which is accommodated in the seal-accommodating space 11.
Accordingly, the seal-accommodating space 11 is arranged between
the link plates 1, 2 and radially outside the bush 3.
The seal-accommodating space 11 serves, in particular, for
accommodating the seal 9 and can be designed in different ways.
In a preferred embodiment, the seal-accommodating space comprises
a thrust washer 7 and an annular cutout 8. It is preferable for the
cutout 8 to be arranged in the outer link plate 2 and for the thrust
washer 7 to be arranged in front of the inner link plate 1. Such an
embodiment is illustrated, in particular, in figures 2 and 3. However, it
is also conceivable, in principle, to have a converse arrangement.
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The thrust washer 7, which could also be referred to as a thrust ring,
preferably has approximately a cross section in the form of a box-like
channel. In other words, as seen in cross section, the thrust washer 7
has a rectilinear base side and two legs extending from the base side,
in particular from the ends thereof. The legs may be of different
lengths. It is also possible for the thrust washer 7 to be shaped in
other ways. For example, it can be a flat configuration, that is to say
with a rectangular cross section. An L-shaped cross section is also
io conceivable.
Provision is preferably made for the bush 3 to be provided with a
projection 31, in other words a projection as a measure from the end
of the bush to the surface of the inner link plate 1, which could also
be referred to as a protrusion and projects from the inner link plate.
The thrust washer 7 is preferably fitted onto said projection,
projecting from the inner link plate 1 and belonging to the bush 3,
and, accordingly, is arranged in front of the inner link plate 1. The
inner radius of the sealing arrangement, in particular of the seal, is
preferably greater than the outer radius of the bush, in particular of
the projection of the bush. The thrust washer 7 is preferably fastened
by a press fit on the bush 3 or the projection 31, or by some other
force-fitting or form-fitting method. In addition to accommodating the
thrust washer 7, the projection 31 can perform the function of a
spacer ring and protects the seal 9 against mechanical overloading.
The annular cutout 8, which could also be referred to as an annular
groove, is likewise in the form of a box-like channel in cross section;
to this extent, the cutout 8 preferably has a base and two side
surfaces perpendicular thereto.
In an installed state, the thrust washer 7 and the annular cutout 8
have their respective openings located opposite one another, and this
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results in a seal-accommodating space 11 between the thrust washer
7 and the annular cutout 8.
As an alternative, the seal-accommodating space 11 can also be
formed by a thrust washer 7 and an accommodating washer 12. In this
case, there is no annular cutout in the link plate. In this case, the
accommodating washer, which could also be referred to as an
accommodating ring, serves predominantly for retaining the seal 9
within the seal-accommodating space 11. Here too, the thrust washer
7 and accommodating washer 12 can optionally be arranged,
respectively, on the inner link plate 1 and outer link plate 2. However,
it is preferable for the thrust washer 7 to be arranged in front of the
inner link plate 1 and for the accommodating washer 12 to be
arranged in front of the outer link plate 2. Such an embodiment is
illustrated in figure 4. In addition, the thrust washer 7, together with
the accommodating washer 12, forms a labyrinth, or a labyrinth seal,
which protects the seal 9.
As a further alternative, it is also possible for the seal-accommodating
space 11 to be formed by an annular cutout 8 and a thrust washer 7
accommodated in an annular cutout 13. It is preferable for the annular
cutout 8 to be provided in the outer link plate 2 and for the annular
cutout 13 with the thrust washer 7 to be provided in the inner link
plate 1. Such an embodiment is illustrated in figure 5. The thrust
washer 7 used here has, for example, an L-shaped cross section.
As a result, in particular in conjunction with the aforementioned
exemplary embodiments, this gives a seal-accommodating space 11,
preferably with a rectangular cross section, which goes around the
region of the bush 3 and/or the projection 31 of the bush. It is
essentially the case that the thrust washer 7 performs the function of
a sealing surface, in other words that surface against which the seal
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presses and is in frictional contact. The seal 9 and the thrust washer
7 and/or machined link-plate surface preferably give an outwardly
oil-tight, but at least predominantly oil-tight, sealing arrangement. It is
possible to use preferably steel, stainless steel or case-hardened
steel for the thrust washer 7. A variety of options are conceivable
here. The elements forming the sealing surface in each case, in other
words the thrust washer 7, should meet a number of requirements.
They should be hardened and finely machined, in order to prevent
rapid wear of the seal, but also of the thrust washer 7 itself. Coating
or some other mechanical machining operation is also conceivable.
The surface roughness of the sealing surface of the thrust washer is
preferably not at a particularly high level. The surface roughness can
be set by suitable machining measures. Ultimately, however, the
machining, and production, of a thrust washer in the form of a sealing
surface is easier than corresponding machining of the link plate to
form a sealing surface. It is also the case here that no particular
attention has to be paid to the selection of the link-plate material in
relation to whether the latter is suitable as the sealing surface, since
the sealing surface is provided by a separate part, in this case the
thrust washer. It is also conceivable for the respective link-plate
surface, instead of the thrust washer, to be machined appropriately in
order to be able to serve as a sealing surface. It is possible here for
the respective link-plate surface to be machined, for example, by
coating, but other machining methods such as hardening, heat
treatment, mechanical machining, etc., are also possible.
The annular cutout 8 or the accommodating washer 12 serves
predominantly for retaining the seal 9 within the seal-accommodating
space.
The seal 9 is preferably a sealing ring or annular seal. The seal 9 is
intended to prevent dirt from penetrating into the chain joint and to
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prevent lubricant/oil from escaping from the chain joint. The seal 9
should have appropriate resilient features so that there is always a
defined amount of contact/pressure between the seal 9 and the
respective sealing surface. This could also be achieved by a separate
resilient element. It is possible for the seal 9 to be, for example, a
seal which comprises 3 components.
In addition to the seal 9, it is also possible for a ring 10, preferably a
metal ring, to be inserted into the seal-accommodating space 11. The
ring 10, for example together with the thrust washer 7 or the leg of the
thrust washer, can form a labyrinth seal. However, a different pairing,
for example together with the annular cutout of the opposite link plate,
is also conceivable. In addition, the ring 10 can function as an
installation aid and/or as mechanical protection for the seal 9. The
bush 3 or the projection 31 contributes to limiting the amount of axial
play by abutment against the outer link plate 2.
As already outlined above, the seal 9 seals the chain joint in a
lubricant-tight manner to a technically feasible extent. To this extent,
the chain joint can be filled with lubricant. Examples of possible
lubricants here are oil and grease.
The lubricant is preferably introduced via lubricant-introduction
openings 43, which can be provided in the bush 3 and/or the pin 4. In
the exemplary embodiment according to figures 2 and 3, for example,
lubricant-introduction openings 43 are provided both in the pin and in
the bush. In the embodiment according to figure 6, for example two
lubricant-introduction openings 43 are provided in both end sides of
the pin 4.
Provision may also be made for the bush 3 and/or the pin 4 to be
provided with lubricant-accommodating devices 44, for example
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grooves, surfaces or bores. It is essentially the case that the
lubricant-accommodating devices 44 serve to keep the lubricant
between the bush 3 and pin 4. It is preferably the case that channels
42 are provided in the pin 4 and the bush 3, between the
lubricant-introduction openings 43 and the lubricant-accommodating
devices 44, it being possible for the lubricant introduced to pass
through said channels to the lubricant-accommodating devices 44.
The lubricant-introduction openings 43 can be closed, for example, by
means of suitable nipples or screws. It is also the case that the
channels 42 as such can serve as reservoirs for lubricant. Ultimately,
the lubricant is distributed within the chain joint.
Provision is preferably also made for the seal-accommodating space
11 to be filled with a lubricant. The lubricant accommodated here
serves essentially as a lubricant reservoir for the chain joint and for
wetting the seal with lubricant. Provision may preferably be made
here for the bush 3 to have radial grooves 32 on the end side. These
grooves 32 allow lubricant to be exchanged between the
seal-accommodating space and the chain joint.
